1. Field of the Invention
The subject matter of this invention relates generally to connections for unit substations and relates more particularly to the type of connections adapted for use during seismic events.
2. Description of the Prior Art
Interconnection of unit substation devices such as transformers and switchgears is well known in the prior art. An example of a prior art interconnection is shown in the Westinghouse Electric Corporation Instruction Paper entitled "Unit Substation Throat Housing," identified by the reference symbols I.L. 48-300-1A, dated July, 1959. FIG. 1 of the latter bulletin is similar to FIG. 1, prior art of the drawings of this application. A duct for interconnecting high voltage devices at a relatively high vertical point on high voltage devices is shown in U.S. Pat. No. 3,515,976, issued on June 20, 1970 to J. Huret et al. Furthermore, connections of bus apparatus are shown in U.S. Pat. No. 3,489,846, issued Jan. 13, 1970 to J. A. Fehr, Jr.; U.S. Pat. No. 3,485,936, issued Dec. 23, 1969 to L. C. Goodridge; and U.S. Pat. No. 3,591,707, issued July 6, 1971 to G. F. Swench et al. The patent of Huret shows a relatively rigid interconnection between spaced high voltage apparatus. The patents to Fehr, Goodridge and Swench show expansion joint systems which are generally adapted for thermal expansion. It would be advantageous if a way could be found to interconnect relatively closely spaced high voltage electrical equipment utilizing the existing electrical output and input terminals of the electrical apparatus in question and using an appropriate seismic tolerant protective bus run structure. It is known that during a seismic event such as an earthquake the relative mass, height, depth, width and other physical characteristics of transformer and switchgear equipment may allow the apparatus to vibrate at different resonant frequencies upon being excited by the earthquake. The vibration may take the form of twisting or translation and may be in many planes or in one plane. The vibration may be such that at any instant of time the various pieces of switchgear equipment are moving towards each other or away from each other or in any number of different modes. It has been determined that one kind of motion which affects the interconnection between the devices occurs in a vertical plane which includes the interconnecting conductors between the devices. Furthermore, a very destructive situation exists when the devices move directly towards each other or directly away from each other. The relative motion tends to cause the interconnecting conductors to break or to cause the housing or bus run to break and interrupt service.